Preparation method of phosphotungstic acid / silicon dioxide catalyst with Janus structure and application of phosphotungstic acid / silicon dioxide catalyst in heterogeneous oxidation reaction

Abstract

The invention provides a preparation method of a phosphotungstic acid / silicon dioxide catalyst with a Janus structure and application of the phosphotungstic acid / silicon dioxide catalyst in a heterogeneous oxidation reaction. The catalyst takes silicon dioxide as a carrier, phosphotungstic acid is loaded on the surface, and an n-octane-anhydrous acetonitrile emulsion system can be effectively stabilized. The catalyst shows efficient catalytic activity in oxidative desulfurization and dye degradation reactions, can promote oxidative removal of dibenzothiophene and degradation of Congo red dye, is suitable for a complex heterogeneous reaction system in the thickened oil recovery and processing process, and has wide industrial application prospects.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oil and gas field chemicals, and particularly relates to a preparation method of a Janus structure phosphotungstic acid / silica catalyst and application of the Janus structure phosphotungstic acid / silica catalyst in a heterogeneous oxidation reaction. BACKGROUND

[0002] Petroleum is an important component of the global energy system. In recent years, the increasing energy demand has led to the continuous depletion of easily exploitable light oil resources, and under this background, heavy oil resources show great development potential, and their exploitation and processing technology has attracted more and more attention.

[0003] However, heavy oil has the characteristics of high viscosity and low flowability, and its exploitation and processing are significantly more difficult than conventional crude oil. Among them, sulfur-containing thiophene compounds are an important factor leading to high viscosity and strong stability of heavy oil, and they are easily converted into sulfur oxides in the processing process, causing environmental pollution. In addition, heavy oil cracking and reforming products, as the main raw materials for fiber production, will generate a large amount of printing and dyeing wastewater in the subsequent processing process. These pollution problems derived from the development and utilization of heavy oil pose a serious threat to human health.

[0004] Oxidation method as a green and economical process has been widely used in desulfurization and dye degradation process. The commonly used oxidants are mostly water-soluble substances, which have mass transfer resistance in oil-water two-phase system and are difficult to fully contact with thiophene compounds in oil phase; on the other hand, the high solubility of oxidants in water phase also increases the difficulty of their recovery in dye wastewater treatment process. These problems not only increase the operation cost, but also limit the treatment efficiency. Therefore, developing a multifunctional oxidation reaction catalyst suitable for complex systems in multiple scenes has important industrial significance for promoting the efficient and clean utilization of heavy oil resources. SUMMARY

[0005] One of the present application provides a preparation method of a Janus structure phosphotungstic acid / silica catalyst, which specifically comprises the following steps:

[0006] 1) Toluene, 3-aminopropyltriethylsilane, tetraethyl orthosilicate, span-80 are mixed according to the mass ratio of 60:(0.92-1.1):5.2:5, then a pH=2.5 aqueous solution containing 1.67wt% Tween-80 is added, and high-speed stirring mixing reaction, ultrasonic crushing, centrifugation, and drying are carried out to obtain product 1;

[0007] 2) The product 1 is dispersed into a methanol solution, phosphotungstate is added to the suspension, and then uniform stirring, reaction, centrifugation and drying are carried out to obtain the catalyst.

[0008] In one specific embodiment, in step 1), the aqueous solution is adjusted to a pH value of 2.5 with 2 mol / L hydrochloric acid.

[0009] In one specific embodiment, in step 1), the high-speed stirring speed is 12500 rpm / min.

[0010] In one specific embodiment, in step 1), the high-speed stirring time is 2.5 min.

[0011] In one specific embodiment, in step 1), the reaction temperature is 70℃.

[0012] In one specific embodiment, in step 1), the reaction time is 12 h.

[0013] In one specific embodiment, in step 1), the ultrasonic crushing time is 30 min.

[0014] In one specific embodiment, in step 2), the suspension is adjusted to a pH value of 2.5 with 2 mol / L hydrochloric acid.

[0015] In one specific embodiment, in step 2), the reaction temperature is 30℃.

[0016] In one specific embodiment, in step 2), the reaction time is 24 h.

[0017] Advantages of the present application:

[0018] The catalyst prepared by the present application can stabilize the emulsion multiphase system of n-octane-acetonitrile under certain conditions, and realize efficient promotion of the oxidative desulfurization of dibenzothiophene in n-octane, and can promote the oxidative degradation of Congo red dye in water under certain conditions, and is suitable for industrial application scenarios of thick oil development and processing. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 The infrared spectrum of the catalyst is shown.

[0020] Figure 2 The scanning electron microscope and transmission electron microscope images of the catalyst are shown.

[0021] Figure 3 The microscopic images of the formation of anhydrous acetonitrile-n-octane emulsion with different mass fractions of catalyst are shown. DETAILED DESCRIPTION

[0022] The present application will be further described below in conjunction with examples, but the examples of the present application are only exemplary descriptions, and the embodiments do not constitute a limitation on the present application in any case.

[0023] Example 1

[0024] Synthesis method of Janus structure phosphotungstic acid / silica catalyst:

[0025] (1) 0.5 g of Tween-80 was dissolved in 30 mL of deionized water, and 2 mol / L HCl was used to adjust the pH value to 2.5 as the aqueous phase. 60 g of toluene, 5.2 g of tetraethyl orthosilicate, 1.1 g of 3-aminopropyltriethylsilane, and 5.0 g of Span-80 were weighed to form a mixed solution. Then the aqueous phase was added to the mixed solution, homogenized at a speed of 12500 rpm for 2.5 min to form an oil-in-water emulsion, and stirred at 70°C for 12 h. Then, the product was centrifuged, dispersed in anhydrous ethanol, and ultrasonically crushed for 30 min. Finally, the product was obtained by centrifugation and freeze-drying.

[0026] (2) 0.2 g of product 1 was dispersed in 50 mL of methanol to form a suspension, and 2 mol / L HCl was used to adjust the pH value to 2.5. 0.77 g of phosphotungstic heteropoly acid was dispersed in 50 mL of methanol, and then the solution was added to the suspension and mixed well. The reaction was carried out under stirring for 24 h, and finally the final catalyst product was obtained by centrifugation and drying.

[0027] Characterization:

[0028] The product 1 and the catalyst were characterized by Fourier transform infrared detection. The KBr tabletting method was used, the product 1 and the catalyst sample were vacuum dried until the mass was constant, about 200 mg of dried KBr powder and about 2 mg of sample powder were weighed into a corundum mortar and mixed and ground to form a powder with an average particle size of about 2 μm, then a tablet press was used to press the sample (pressure about 12 MPa) to obtain a transparent sheet for detection. The detection conditions: wavelength range is 500-4000 cm -1 , resolution is 2 cm -1 . The results are shown in Figure 1 .

[0029] From Figure 1 , it can be seen that 802.34 cm -1 is the Si-O stretching vibration peak, 1106.15 cm -1 is the anti-symmetric stretching vibration peak of Si-O-Si. 2923.09 cm -1 and 2855.12 cm -1 are the asymmetric and symmetric stretching vibration peaks of -CH2, indicating the successful preparation of product 1. 983.49 cm -1 and 897.26 cm -1 are the specific vibration peaks of W=O and W-O-W, respectively, indicating the successful preparation of the catalyst.

[0030] The morphology of the catalyst was photographed by scanning electron microscopy and transmission electron microscopy. The results are shown in Figure 2 .

[0031] As can be seen from Figure 2 , the final catalyst product has a two-dimensional sheet structure, and the morphology of one side of the surface is rough, and the other side is smooth, which proves the effective synthesis of its Janus structure.

[0032] Example 2

[0033] Emulsion performance test of Janus structured phosphotungstic acid / silica catalyst:

[0034] 1. Emulsion preparation and water separation rate calculation

[0035] 0.025 g, 0.05 g, 0.075 g and 0.1 g (mass fraction of 0.25wt%, 0.5wt%, 0.75wt% and 1wt%) of catalyst were respectively weighed and dispersed in 5 g of anhydrous acetonitrile, then 5 g of n-octane and 100 ppm of 30wt% H2O2 were added, and a pichia emulsion was obtained by ultrasonic cell crusher at 25°C and 300W for 5 min.

[0036] 2. Emulsion micrography

[0037] About 1.5 mL of the prepared pichia emulsion was placed on a glass slide, and the micro-morphology of the anhydrous acetonitrile-n-octane pichia emulsion particles was observed by metallographic microscope. The results are shown in Figure 3 .

[0038] As can be seen from Figure 3 , the addition of catalysts with different mass fractions can form pichia emulsions with different states, and the emulsion particles can be clearly observed, and the average size of the emulsion particle diameter decreases (from 65.62 μm to 15.87 μm) as the catalyst mass fraction increases (from 0.25wt% to 1wt%).

[0039] 3. Calculation of emulsion water separation rate

[0040] The obtained emulsion was poured into a 15 mL graduated cylinder and left to stand, and the volume of the pichia emulsion was recorded at different times (15 min, 30 min, 45 min, 60 min, 75 min and 90 min). The emulsification index (EI) of the emulsion was calculated by formula (1)

[0041]

[0042] wherein V e represents the volume of the emulsion in the mixed system, and V owVolume of n-octane and anhydrous acetonitrile added initially.

[0043] The higher the EI value of the emulsion, the higher the content of the emulsion in the system, and the more stable the emulsion.

[0044] The test results of the stability (emulsion index) of the emulsion are shown in Table 1.

[0045] As can be seen from Table 1, the emulsion index of the emulsion decreases with the extension of the standing time, and increases with the increase of the mass fraction of the emulsifier.

[0046] Table 1

[0047] 0.25 wt% 0.50 wt% 0.75 wt% 1.00 wt% 15 minutes 75.23 77.16 83.58 86.25 30 minutes 73.19 74.88 81.30 83.87 45 minutes 70.55 73.65 80.17 82.64 60 minutes 67.74 72.14 78.66 81.03 75 minutes 65.95 71.91 78.33 80.53 90 minutes 65.22 71.74 78.26 80.43

[0048] Example 3

[0049] Test of the oxidative desulfurization performance of the Janus structured phosphotungstic acid / silica catalyst:

[0050] 1. Construction of the Pickering emulsion catalytic oxidative desulfurization system

[0051] 0.075 g (0.75 wt% mass fraction) of the catalyst was weighed and dispersed in 5 g of anhydrous acetonitrile, followed by the addition of 5 g of n-octane (1000 ppm of dibenzothiophene was dispersed therein) and 60 ppm of 30 wt% H2O2, and the Pickering emulsion was obtained by emulsification with an ultrasonic cell crusher at 25°C and 300 W for 5 min. The oxidative desulfurization reaction was carried out at different temperatures (45°C, 55°C, 65°C and 75°C) for 90 min.

[0052] 2. Calculation of the desulfurization rate of the system

[0053] 0.5 mL of the reaction mixture was extracted from the Pickering emulsion system at different times (15 min, 30 min, 45 min, 60 min, 75 min and 90 min) for centrifugal demulsification, and the upper oil phase was collected. The oil phase composition and the content of dibenzothiophene were determined by gas chromatography-mass spectrometry. The desulfurization rate of the system was calculated by formula (2)

[0054]

[0055] The desulfurization rates of the Pickering emulsion oxidative desulfurization system at different temperatures are shown in Table 2.

[0056] As can be seen from Table 2, the catalytic system can achieve effective desulfurization, and the desulfurization rate of the system increases with the extension of the reaction time and the increase of the temperature.

[0057] Table 2

[0058]

[0059]

[0060] Example 4

[0061] Performance test of catalytic oxidative degradation of dyes by Janus structured phosphotungstic acid / silica catalyst:

[0062] 1. Construction of Fenton-like catalytic oxidative degradation of dye system

[0063] 0.0075 g (0.075 wt%) of catalyst was weighed and dispersed in 10 mL of deionized water (100 ppm of Congo red was dispersed inside), and after standing for 30 minutes to reach adsorption-desorption equilibrium, 300 ppm of potassium persulfate was added to initiate the degradation reaction. The oxidative degradation reaction was carried out at different pH values (6, 8, 10 and 12), and the reaction time was 30 min.

[0064] 2. Calculation of Congo red removal rate

[0065] At different times (5 min, 10 min, 15 min, 20 min, 25 min and 30 min), 0.5 mL of the reaction was extracted from the mixed system, centrifuged and the supernatant was collected. The absorbance of the supernatant was measured at 497 nm wavelength using ultraviolet-visible spectrophotometry. The removal rate of Congo red in the system was calculated by formula (3)

[0066]

[0067] The removal rate of Congo red by Fenton-like catalytic oxidative degradation of Congo red system at different pH values is shown in Table 3.

[0068] As can be seen from Table 3, the catalytic system can achieve effective removal of Congo red, and the removal rate of Congo red in the system increases with the extension of the reaction time, and increases with the decrease of pH.

[0069] Table 3

[0070] pH = 6 pH = 8 pH = 10 pH = 12 5 minutes 96.75 93.50 90.21 85.88 10 minutes 97.56 93.90 90.51 87.96 15 minutes 98.20 94.68 91.22 88.92 20 minutes 98.79 95.34 91.75 89.96 25 minutes 99.29 95.89 91.99 90.10 30 minutes 99.31 95.90 92.07 90.19

Claims

1. A catalyst for improving oxidation reaction efficiency in multiple systems, characterized in that, The catalyst is phosphotungstic acid supported silica-based Janus nanosheet, which has better catalytic performance in both homogeneous and heterogeneous systems.

2. The catalyst according to claim 1, characterized in that, The catalyst can stabilize the Pickering emulsion formed by anhydrous acetonitrile and n-octane under certain conditions.

3. The catalyst of claim 1, wherein The catalyst can realize efficient desulfurization of dibenzothiophene in the Pickering emulsion of claim 2 under certain conditions.

4. The catalyst of claim 1, wherein The catalyst can realize efficient removal of Congo red dye in water under certain conditions.

5. A preparation method of the catalyst according to claim 1, 2, 3 or 4, comprising the following steps 1) mixing toluene, 3-aminopropyltriethylsilane, tetraethyl orthosilicate and span-80 according to the mass ratio of 60:(0.92-1.1):5.2:5, then adding a water solution containing 1.67wt% Tween-80 with pH=2.5, mixing under high-speed stirring, reacting at 70℃ for 12h, ultrasonic crushing, centrifugal drying to obtain product 1; 2) dispersing product 1 into methanol solution, adding adjustable amount of phosphotungstic heteropoly acid into the suspension, mixing, stirring at a constant speed, reacting at 30℃ for 24h, centrifugal drying to obtain the catalyst.

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